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OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012

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The current is the flow of electrons. The voltage is like the 'pushing force' that pushes electrons around. However the e.m.f is the voltage when no current flows. :smile:

can you help me on this question please on how to balance the ionic equations :-

Fe2+ +o2 + H+ gives Fe3+ + H20 ?
how would you tackle these?

Reply 1041

Swifttt

Original post by arvin_infinity

I found it OK..are u sure? emm between Mg and Ca which one is larger(well in terms of ionic radius)!!!:O

am almost pretty sure Ca has a larger ionic radius- which is opposite to what MS says

havent got as far as the other question

but also somewhere eles they messed up a calculation insted of getting 0.013 they got 0.13

No just looked again it's definitely right. It says Mg2+ is smaller thus greater charge density, greater attraction, more exothermic LE etc.

I think where you are looking is maybe at 4)a)i), which wasn't the one about Magnesium. 4)c) was, and I'm pretty sure the markscheme is right there.

Yeah I found it fairly hard, got 79/100, but hated the last question where they just lumped like 20 marks into one. I haven't parrot learnt all the colours yet.

Reply 1042

Kae10

Original post by Tyles

explain pleeeeeeeeeeease :colondollar:

Do u understand that the HCL had been divided by a factor of 4 ( from 25 to 100x4), therefore the new concentration is 0.02/4, hence the pH is -log(0.02/4)=2.30

Reply 1043

Robpattinsonxxx

Original post by otrivine

can you help me on this question please on how to balance the ionic equations :-

Fe2+ +o2 + H+ gives Fe3+ + H20 ?
how would you tackle these?

1. balance o's on RHS
2. balance h's on LHS
3. balance charges by adding e- to LHS or RHS

:smile:

Reply 1044

Kae10

Original post by otrivine

can you help me on this question please on how to balance the ionic equations :-

Fe2+ +o2 + H+ gives Fe3+ + H20 ?
how would you tackle these?

First write out the balanced equations in terms of electron transfer for each element. and continue from there, balnace number of electrons first and then it should be okae!

Reply 1045

otrivine

Original post by Robpattinsonxxx

1. balance o's on RHS
2. balance h's on LHS
3. balance charges by adding e- to LHS or RHS

:smile:

thank you

one thing i am ready to taken the test for module 3 where is the page so i can tackle the questions :biggrin:

Reply 1046

Dreamweaver

Anyone know of websites with loads of legacy papers?

Reply 1047

arvin_infinity

A quick question

say you have

E=+1.35 for A+B<=>2C + 2e

if you multiply all species by 2

E would still be the same right?

Reply 1048

mushy1993

construct redox equations for:
aq S2O3(2-) is oxidised to SO4(2-) when it is reacted with chlorine gas which is reduced to chloride ions.

this questions on the main book practice question 2.2 5bii)
what method can I use to tackle this question?
thank you.

Reply 1049

Dreamweaver

Original post by arvin_infinity

A quick question

say you have

E=+1.35 for A+B<=>2C + 2e

if you multiply all species by 2

E would still be the same right?

Yes emf doesn't change unless you change the concentrations.

Reply 1050

arvin_infinity

Original post by Dreamweaver

Yes emf doesn't change unless you change the concentrations.

Phew...

Ermm..
I know o2 is manufactured by the decomposition of H2o2 but wat about H2-how is H2 manufactured?
Vaguely remember As stuff :s-smilie:

Reply 1051

Robpattinsonxxx

Original post by arvin_infinity

Phew...

Ermm..
I know o2 is manufactured by the decomposition of H2o2 but wat about H2-how is H2 manufactured?
Vaguely remember As stuff :s-smilie:

Electrolysis of water or reacting methane with steam.

Reply 1052

arvin_infinity

Original post by Robpattinsonxxx

Electrolysis of water or reacting methane with steam.

That's it

Anyone has some good detailed notes on Hydrogen half cells

Reply 1053

Robpattinsonxxx

WHat would you like to know? :smile:

Reply 1054

Dreamweaver

Original post by arvin_infinity

That's it

Anyone has some good detailed notes on Hydrogen half cells

Attached.

08fcell.pdf66.4KB

Reply 1055

otrivine

can someone explain to me in transition metals we got this en thing
(co(en)3)3+
how would we show it like in en the amines

Reply 1056

Robpattinsonxxx

en is just :NH2CH2CH2NH2: ethane-1,2-diamine. So Co will be in middle and three of the 'en' round the outside. form optical complexes.

Reply 1057

lukas1051

Any predictions for what might come up? I know they usually include a bit of everything, but anything specific they haven't really tested yet?

Reply 1058

Killjoy-

Original post by lukas1051

Any predictions for what might come up? I know they usually include a bit of everything, but anything specific they haven't really tested yet?

My teacher talked of K_stab coming up.

Reply 1059

otrivine

Original post by Robpattinsonxxx

1. Definition of a d block element [1]
2. Configurations of copper and chromium [2]
3. Colour changes in precepitation reactions of Cu2+, Co2+, Fe2+ and Fe3+ with NaOH [4]
4. How do transition metals act as catalysts? [3]
5. When do complexes form square planar? [1]
6. Give an example of a bidentate ligand [1]
7. Describe the action of cis platin and give its complex formula [4]
8. What is a multidentate ligand? [1]
9. Colour changes in ligand substitution reactions using [Cu(H2O)6] with ammonia and chloride ions and [Co(H2O)6] with chloride ions [3]
10. What is ligand substitution? [1]
11. What is kstab? [1] What does a larger kstab value tell you? [1]
12. Describe colour changes in redox titrations using MnO4- /Fe2+ and I2/S2O32-. Give equations of the titrations [5]

Out of 28 :smile:

1) d block is where the electrons occupy the d sub shell
2)cu=1s2,2s2,2p6,3s2,3p6,4s1,3d10
cr= 1s2,2s2,2p6,3s2,3p6,4s1,3d5
3)cu2+ = from pale blue solution to deep blue ppt
co2+ pink - blue
fe2+ = pale green-blue-rust brown on surface
fe3+ = forms rusty brown ppt from blue
4)variable oxidation states, adsorption onto surface , absorption, regenrated and
contact process,harber process,addition of hydrogen
5)with plantium complexes such as (pt(nh2)2cl2) zero charge
6)is it with the en that forms with a transition metal ion
7)binds to dna and prevents cells from dividing and a complex (pt(nh3)cl2)